roundel

noun

• 1a small disk, especially a decorative medallion.
• a picture or pattern contained in a circle.
• Heraldry a plain filled circle as a charge (often with a special name according to color).
• British a circular identifying mark painted on military aircraft, as, for example, the red, white, and blue of the RAF.

• 2a short poem consisting of three stanzas of three lines each, rhyming alternately, with the opening words repeated as a refrain after the first and third stanzas. The form, a variant of the rondeau, was developed by Swinburne.